PARREYSIA 1 143 



''This species varies considerably in form and sculpture. 

 Some specimens are much longer than others, and the amount 

 of corrugation towards the umbones varies considerably. Some 

 examples are ahnost entirely smooth, whereas occasionally the 

 wrinkhng may extend over two-thirds of the surface. The 

 valves are white beneath an olive-brown periostracum, which 

 almost invariably exhibits one or more green rays down the 

 hinder slope. There is in most specimens a kind of lunule in 

 front of the umbones, which varies much in shape, being quite 

 broad and diamond-shaped in some shells and quite narrow 

 and linear in others. An elongate example is 29 mm. in length 

 and 14 in height. A shorter is 20.5 long and 12.75 high." 



Parf.yssia hunanivNSis Haas. 



"Shell very inequilateral, solid, thick. Anterior end very 

 short, semi-circular ; ventral margin slightly convex or angu- 

 lated, posterior end long, biangulate. Beaks situated at 31-100 

 of the total length, much swollen, incurved ; beak sculpture con- 

 sisting of two, radial, strong ribs, which unite at the apex. 

 The anterior extends in the direction of the deepest point of 

 the ventral margin, but does not reach it ; it is tuberculate and 

 may be broken up into a series of distinct tubercles ; the pos- 

 terior extends to the lower angle of the posterior end, where 

 it becomes almost flat and is tuberculate only towards the 

 beaks. The anterior part of the beaks shows weak, slightly 

 raised, radial, somewhat undulating strise. Ligament short. 

 Dorsal slope low, oblique, with a faint line that extends from 

 the beak to the upper angle of the posterior point. Hinge 

 strong, cardinal tooth of the left valve divided by a rectangu- 

 lar, deep groove, jagged, striate, compressed, between the car- 

 dinal and laterals, which meet at a decided angle, there is a 

 long interval ; laterals short, strong ; the cardinal teeth make 

 an angle of about 30° and the laterals one of 15° with the 

 axis of the shell. The anterior muscular impression deep, 

 funnel-shaped, the posterior not. Nacre of a magnificent blu- 

 ish-white. Epidermis chestnut-'brown with yellowish-brown 

 rays, mostly worn off on the umbones. 



